Synthetic lubricant



Patented July 3, 1951 SYNTHETIC LUBRICANT Paul V. Smith, Jr., Westfield,N. J .,'and Alexander H. Popkin, New York, N. Y., assignors to StandardOil Development Company, a corporation of Delaware No Drawing.Application November 27, 1948, Serial No. 62,418

6 Claims.

I This invention relates to a new class of compounds which have beenfound to be particularly suitable for use as synthetic lubricantsbecause of their low pour points and high vis- V cosity indices.

In the lubricant art, considerable progress has been realized in recentyears in the production of lubricants characterized by one or morespecific properties and adapted for particular uses. In the main, thisprogress can be attributed to two developments: the first, new refiningprocedures, and the second, addition agents capable of impartingparticular properties to available lubricants. Thus, viscosity indeximprovers and pour depressants are added to automotive lubricants torender the lubricants more adaptable to wide changes in temperatureconditions, while other agents are added to improve the load carryingproperties of a lubricant which is to be employed, for example, underextreme pressure conditions.

Recently, in an effort to obtain superior lubricants endowed withspecific and superior characteristics, a new field has been explored,namely the synthesis of lubricants from various materials. Estersrepresent one class of materials which have attracted unusual interestas synthetic lubricants. In general, they are characterized by higherviscosity indices, lower pour points, and higher flash points thanmineral oils of corresponding viscosity. The esters described in thepresent specification have been found to exhibit high viscosity indicesand in many cases very low pour points. Those esters which do notexhibit a pour point which is sufficiently low for use without additivemay be made useful by simply adding a pour depressant, as in the case ofmineral oils. The esters possessing both high viscosity indices and lowpour points are of special value in the lubrication of engines which aresubjected to high temperatures such as combustion turbine engines,particularly those of the prop-jet type. Mineral oil lubricantscontaining added viscosity index improvers, thickeners or other highlynonvolatile additives are undesirable for use in such engines because ofthe tendency to leave a residue which accumulates and interferes withthe operation of the engine. A synthetic lubricant of the type describedin the present specification is especially adapted to use under suchconditions, since the lubricant contains no additives and thus tends toleave no residue upon volatilization.

The new compounds of the present invention which have been found to beparticularly suitable for use as lubricating oils are esters ofdicarboxylic acids which contain one or more atoms of oxygen and/orsulfur in ether or thioether linkages, and in which the alcohol residueis a long chain aliphatic hydrocarbon radical ora hydrocarbon radicalcontaining oxygen and/or sulfur in ether or thioether linkages. Moreprecisely, the new class of compounds may be defined by the generalformula where R is an organic group which consists of hydrocarbonradicals interlinked by at least one atom of oxygen and/or sulfur, thetotal number of carbon and oxygen or sulfur atoms in the group beingfrom 3 to and the number of sulfur atoms being not greater than 2. Inthis group there is at least one carbon atom between each carboxyl groupand the nearest oxygen or sulfur atom and at least two carbon atomsbetween any two oxygen and/or sulfur atoms. The hydrocarbon radicals ingroup R may be of any hydrocarbon type, whether aliphatic,cycloaliphatic, aromatic, or aliphatic-aromatic, whether straight orbranched, and whether saturated or unsaturated, although compounds inwhich such hydrocarbon radicals are saturated aliphatic radicals aregenerally preferred. Rand R" of the formula are organic groups, alike orunlike, and may consist of aliphatic hydrocarbon radicals containing atotal in the two groups of 16 to 40 carbon atoms, or they may be groupseach consisting of a series of saturated aliphatic hydrocarbon radicalsinterlinked by l to 5 oxygen 3 V and/or sulfur atoms (not more than 2sulfur atoms), the total number of carbon, oxygen, and sullur atoms inthe two groups being from 8 to 40. When the groups contain oxygen orsulfur atoms, there should be at least two carbon atoms between any twosuch non-carbon atoms and between the carboxyl group and the nearestatom of oxygen or sulfur. The hydrocarbon group at the end of a chainmay contain one or more carbon atoms. To produce a composition whichwill have a sufficiently high viscosity to be useful as a lubricant thecomponents of thecomposition should be chosen so that the molecularweight thereof is at least 300. It is also preferable to preparecompounds having a viscosity not greater than 150 seconds (Saybolt) at210 F.

The esterification process can be carried out by the usual methods,preferably employing anesterification catalyst, such as p-toluenesulfonic acid, and a water-entraining agent.

Illustrative examples of the dibasic acids which may be employed in thesynthesis of the esters of the present invention are the following:diglycolic acid, thiodiglycolic acid, ethylene-bis-glycolic acid,s-oxydipropionic acid, o-di(2-thia-4- carboxybutyDbenzene,4,7-di-oxa--l,10-decanedioic acid,4,7,10,13-tetra-oxa-1,16-hexadecanedloic acid,4,10-di-oxa-7-thia1,13-tridecanedioic acid,4,7,10,13,16-penta-oxa-1,19-nonadecanediic acid, and4,7-di-thia-1,10-decanedioic acid.

In addition to the above, it has been found advantageous to prepareesters from dibasic acids which are addition products of unsaturateddibasic acids and alcohols or mercaptans or of monobasic hydroxy and/ormercapto aliphatic acids and diolefins. For example, two mols ofthioglycolic acid and one mol of cyclopentadiene may be reacted togetherto form a product probably having a composition of the type and such anacid may be reacted with alcohols to form esters suitable for use inaccordance with the present invention. Similarly, thioglycolic acid maybe reacted with vinyl cyclohexene or other diolefins. In a similarmanner, addition products may be formed between unsatu rated acids, e.g., maleic acid, and alcohols or mercaptans. The addition product of amaleic acid ester and dodecyl mercaptan is an example.

CHzSCHzCHzC O OH CHzS C'HzCHaC O OH The monohydric alcohols employed inesteritying the dibasic acids described above are typifled by thefollowing:

Methyl alcohol Ethyl alcohol n-Propyl alcohol I I n-Butyl alcoholIsobutyl alcohol n-Amyl alcohol Isoamyl alcohol n-Octyl alcohol2-ethy1hexyl alcohol Cetyl alcohol Oleyl alcohol Ethylene glycolmono-n-butyl ether Ethylene glycol mono-2-ethylbutyl ether Ethyleneglycol mono-2-ethylhexyl ether Many of the above listed ether alcohols,formed by the reaction of ethylene oxide or propylene oxide withaliphatic alcohols, are known in the industry as Dowanols, Carbitols, orCellosolves.

A group of alcohols especially adapted for. use in connection with thepresent invention are the so-called Oxo alcohols, prepared by thereaction of carbon monoxide and hydrogen upon the olefins obtainablefrom petroleum products and hydrogenation of the resulting aldehydes.Materials such as diisobutylene and C1 olefins are suitable for thispurpose; also higher molecular weight olefinic materials are sometimesemployed. Thev alcohols obtained in this manner are primary alcohols andnormally have a branched chain structure.

In the table below will be shown data obtained in tests of theproperties of severaltypical esters illustrating the present invention.The esterification process was carried out in each case by the followingprocedure: A mixture of I one mol of dlbasic acid, 2.2 mols' of alcohol,0.5 weight percent of p-toluene-sulfonic acid monohydrate, and to 200mls. of a water-entraining agent such as naphtha, benzene, toluene orthe like, is refluxed until no more water is collected in anesterification water trap. The product is washed untilneutral withsaturated aqueous NazCOs solution'and then with water. After drying overa desiccant, such as anhydrous CaSO4, the material is stripped at apressure of 5 mm. to a bath temperature of, 200-225 C.

5 The data obtained in the tests of properties of the esters obtained asdescribed are shown in the following table:

. 6 two carbon atoms between each pair 01' said oxygen atoms and atleast one carbon atom between the carboxyl group and the nearest of saidoxygen I Kinematic Components of Ester Flash Viscosity AqTM A Point,cosity Z F. Index Acid Alcohol 100 F. 210 F.

Diglvoolic 410 16. 360 3. 696 0. 731 130 80 Do 390 21. 840 4. 083 0. 77391 -35 fl-0xydlprop1omc 25. 540 5. 298 0 673 150 -35 o 415 226.000 25160 0565 1'26 Ethvlene-bis-glycohc 445 19 230 6'000 0'41 120 4 I D o 44023. 950 4. 590 0. 732 121 35 4,7-D1-oxa-Ll0demne-d1o1c 012-011 "0x9 41022. 97 4. 97 0.672 155 0 Do Butvl Carbltol. e 16. 600 3. 962 0. 094 158-35 4,7,10,13-letra-oxa-l,l6-hexadecaned1olc... C 0110". 355 13.700 3.487 0. 702 154 -35 4,7,10,l3,16'le11taoxa-1,lll-nonadecanedioie do. 32.610 6. 578 0. 634 152 Q-35 Th1od1p1-op1on1c 2-E t hvlbexyl 11. 596 2.911 0. 760 113 -35 D0 C3 OX0" 13. S90 3. 480 O. 710 148 (-35 D0. C6 "OX01' 18. 410 4. 133 0. 705 148 35 Em Cm OX0 19. 880 4.38 0 695 152 (-35Ds- 266124101? 11-16 4-64 8233 11: 43-1114: emne411616 But vl 26. 5805:449 0' 670 149 2 filil'ggciioxaJ-thiaq,13-tr1decaned1o1c 01 0x0 22.840 4. 782 0. 692 146 -35 2 111615 T1116 lycolic 1 ml lsopngle }n-Decyl32. 210 s. 973 0.681 133 35 Adduct:1 Th 8] 1 2mos io ycoic 1. d m1cyclopemadiene do 19. 660 4. 306 0. 703 14s 35 not: 2 mols 'Ihioglycolic1 mo] Vinylcyclohexene 2L4) 680 0'683 154 35 Adduct:l Th

1 mo colic 1 mm undgglenic }Isoamyl 415 13. 990 3. 642 0. 683 167 --10Adduct:I Th 1 1 1 mo 10 00 ie 1 mo] g gf }Butyl Carbltol 20. 660 4. 7220. 666 164 -35 Adduct:l Th 1 1 1 1 mo 1 m0] if gg g }Butyl Cellosolve16.55 4. 061 0.677 169 5 Adduct:l Th 1 l 1 mo 10 co ic M 1 mol 5}: }c"0X0" 455 30.610 5.993 0.664 146 -15 duct:

1 mol Maleic 1 m0] mDodecYlmercaDtan }n-Decanol 475 24. 760 s. 156 0.676 150 Adductzl M I 1 mo a eie v 1 m0] mDodecmmercaman }C1 OX0 460 23.970 4. 742 0. 714 133 25 Adduct:l M l 1 mo a eie 'Iri ro ylenc 2] colmonois 1 mol n-Dodecylmercaptan $1 e ther. 3 0pm 355 91 31 683 120 5Adduct' D 1 11161 Itaco 16 Add mmgecylmemman }01 "0x0 440 32v 010 5.8820. 697 131 uc 1 mol Itaconic 1 m0! n Dodecyl mercaptamuu }Butyl Carb1tol415 55. 950 9. 822 0.599 144 Adduet:1 I

1 mo taconic 1 Ma 2 tert D0decy1 mmamm }c11-O11 "0x0 s95 50. 84 v. 63 0.689 -3 I10 I 1 mol Iteconic Tri r0 vlene 1 col monois 1 mo] tert=Dodecylmercapta p51 -her. g y 0pm 360 1349 754 71 5 Adduct:l O]

1 mo clc I mo1 Thiog1yc0nc }Butyl Carbltol 460 31. 780 6. 471 o. 634 15a10 0-D1(2-th1a4-carboxy-butyl) b C C12n 0110" 27. 660 5.197 0.709 131 40The above data indicate that the esters constituting the subject matterof the present invenmay also be blended with mineral lubricating oils C0to give lubricants of improved viscosity index and pour point.

What is claimed is:

1. As a new composition of matter a compound of the formula 65 where Ris an organic group consisting of sat- 7i urated aliphatic hydrocarbonradicals interlinked by at least two oxygen atoms, the total number ofcarbon and said oxygen atoms in the group R being from 3 to 85, thenumber of oxygen atoms being at least 2, in which there are at least 7.1

atoms; where R and R are organic groups selected from the classconsisting of (1) saturated branched chain aliphatic hydrocarbonradicals containing a total in the two groups of 16 to 40 carbon atomsand (2) radicals consisting of a series of saturated aliphatichydrocarbon radicals linked through 1 to 5 non-carbon atoms in eachgroup of the class of elements consisting of oxygen and sulfur, thenumber of sulfur atoms being not greater than 2, and the total number ofcarbon and said non-carbon atoms in the two groups R and R" being from 8to 40, there being at least 2 carbon atoms between each pair of saidnon-carbon atoms and between the carboxyl group and the nearest suchnon-carbon atom; the components of the composition being so chosen thatthe molecular weight thereof is at least 300.

2. A composition according to claim 1 in which the groups R and R" areeach saturated branched chain aliphatic hydrocarbon radicals and containa total in the two groups of 16 to 40 carbon atoms.

3. A composition according to claim 1 in which each of the groups R, andR" consists of a series oi. saturated aliphatic hydrocarbon radicalslinked through 1 to 5 non-carbon atoms of the class of elementsconsisting of oxygen and sulfur.

4. As a new composition of matter the ester formed by reacting onemolecular proportion 4,7-di-oxa-1,10-decanedioic acid and two molecularproportions of butyl carbitol.

5. As a new composition of matter the ester formed by reacting onemolecular proportion of 4,7,10,13 tetra-oxa 1,16 hexadecanedioic acidwith two molecular proportions of Ca "Oxo alcohol.

6. As a new composition of matter the ester formed by reacting onemolecular proportion of 4,7,10,13,16-penta-oxa-1,19-nonadecanedioic acidwith two molecular proportions of Ca 0x0 alcohol.

PAUL V. SMITH, JR. ALEXANDER H. POPKIN.

8 REFERENCES cn'En The following references are of record in the- NumberName Date 2,063,620 Persiel Dec. 8, 1936 2,262,686 Kyrides Nov. 11,19412,283,764 Rosefibach May 19, 1942 2,327,652 Kyrides Aug 24, 19432,341,846 Meincke Feb. 15, 1944 2,347,627 Bruson Apr. 25, 1944 2,393,327Langkammerer Jan. 22, 1946 2,425,225 Bearse Aug. 5, 194! 2,468,725Gresham May 3, 1949 2,469,317 Shokal May 3, 1949

1. AS A NEW COMPOSITION OF MATTER A COMPOUND OF THE FORMULA